US10728081B1ActiveUtility
Wideband TX IQ imbalance estimation
Est. expiryMar 15, 2039(~12.7 yrs left)· nominal 20-yr term from priority
H04L 27/364H04L 27/0014H04L 27/2657H04L 2027/004H04L 27/3863H04L 2027/0042
87
PatentIndex Score
10
Cited by
12
References
17
Claims
Abstract
A computer-implemented method of estimating IQ imbalance in a communication system including a transmitter and a receiver. The method includes: defining a system model in which a transmitted signal is affected by TX IQ imbalance, carrier frequency offset (CFO) and RX IQ imbalance; controlling a local oscillator at the transmitter to introduce a known carrier frequency offset (CFO) during a calibration; and estimating unknown parameters in the system model using a pre-defined training sequence to determine the TX IQ imbalance and the RX IQ imbalance.
Claims
exact text as granted — not AI-modifiedThe invention claimed is:
1. A method of estimating in-phase and quadrature (IQ) imbalance, the method at least partially performed by electronic circuitry and comprising:
defining a system model in which a transmitted signal is affected by transmitter IQ (TX IQ) imbalance, carrier frequency offset (CFO) and receiver IQ (RX IQ) imbalance;
controlling a local oscillator at the transmitter to introduce a known carrier frequency offset (CFO) during a calibration; and
estimating unknown parameters in the system model using a pre-defined training sequence to determine the TX IQ imbalance and the RX IQ imbalance,
wherein the CFO is chosen to provide a relative frequency offset of at least 0.001, at least 0.005 or at least 0.05.
2. A method of estimating in-phase and quadrature (IQ) imbalance, the method at least partially performed by electronic circuitry and comprising:
defining a system model in which a transmitted signal is affected by transmitter IQ (TX IQ) imbalance, carrier frequency offset (CFO) and receiver IQ (RX IQ) imbalance;
controlling a local oscillator at the transmitter to introduce a known carrier frequency offset (CFO) during a calibration; and
estimating unknown parameters in the system model using a pre-defined training sequence to determine the TX IQ imbalance and the RX IQ imbalance,
wherein the TX IQ imbalance is defined as
y
k
,
l
(
i
)
=
α
k
(
T
)
(
i
)
x
k
,
l
(
i
)
+
β
-
k
(
T
)
*
(
i
)
x
-
k
,
l
*
(
i
)
where k indicates a subcarrier, l indicates a time index, i=1, . . . , N tx is a transmit channel index and α k (T) , β k (T) are IQ imbalance coefficients at the transmitter.
3. A method of estimating in-phase and quadrature (IQ) imbalance, the method at least partially performed by electronic circuitry and comprising:
defining a system model in which a transmitted signal is affected by transmitter IQ (TX IQ) imbalance, carrier frequency offset (CFO) and receiver IQ (RX IQ) imbalance;
controlling a local oscillator at the transmitter to introduce a known carrier frequency offset (CFO) during a calibration; and
estimating unknown parameters in the system model using a pre-defined training sequence to determine the TX IQ imbalance and the RX IQ imbalance,
wherein the system model further comprises an inter-channel interference defined as
z
k
,
l
(
m
)
=
∑
i
=
1
N
tx
h
k
(
m
,
i
)
y
k
,
l
(
i
)
where m=1, . . . , N rx is a receive channel index and h is a channel coefficient.
4. A method of estimating in-phase and quadrature (IQ) imbalance, the method at least partially performed by electronic circuitry and comprising:
defining a system model in which a transmitted signal is affected by transmitter IQ (TX IQ) imbalance, carrier frequency offset (CFO) and receiver IQ (RX IQ) imbalance;
controlling a local oscillator at the transmitter to introduce a known carrier frequency offset (CFO) during a calibration; and
estimating unknown parameters in the system model using a pre-defined training sequence to determine the TX IQ imbalance and the RX IQ imbalance,
wherein the CFO is defined as
w k,l ( m )= e jϕl z k,l ( m )
where ϕ represents a phase shift caused by the CFO.
5. The method of claim 4 wherein the RX IQ imbalance is defined as
r
k
,
l
(
m
)
=
α
k
(
R
)
(
m
)
w
k
,
l
(
m
)
+
β
-
k
(
R
)
*
(
m
)
w
-
k
,
l
*
(
m
)
where α k (R) , β k (R) are IQ imbalance coefficients at the receiver.
6. The method of claim 5 wherein the system model is defined as
r
k
,
l
=
(
e
j
ϕ
l
A
k
+
e
-
j
ϕ
l
B
k
)
x
k
,
l
+
(
e
j
ϕ
l
C
k
+
e
-
j
ϕ
l
D
k
)
x
-
k
,
l
*
where r k,l is a N rx ×1 vector, A k ,B k ,C k ,D k are N rx ×N tx matrices and y k,l is a N tx ×1 vector.
7. The method of claim 6 wherein the matrices are defined as:
A
k
(
m
,
i
)
=
h
k
(
m
,
i
)
α
k
(
T
)
(
i
)
α
k
(
R
)
(
m
)
B
k
(
m
,
i
)
=
h
-
k
*
(
m
,
i
)
β
k
(
T
)
(
i
)
β
-
k
(
R
)
*
(
m
)
C
k
(
m
,
i
)
=
h
k
(
m
,
i
)
β
-
k
(
T
)
*
(
i
)
α
k
(
R
)
(
m
)
D
k
(
m
,
i
)
=
h
-
k
*
(
m
,
i
)
α
-
k
(
T
)
*
(
i
)
β
-
k
(
R
)
*
(
m
)
.
8. The method of claim 7 wherein the TX IQ imbalance is obtained from
C
k
(
m
,
i
)
A
k
(
m
,
i
)
=
β
-
k
(
T
)
*
(
i
)
α
k
(
T
)
(
i
)
.
9. The method of claim 7 wherein the RX IQ imbalance is obtained from
D
k
(
m
,
i
)
A
-
k
*
(
m
,
i
)
=
β
-
k
(
R
)
*
(
i
)
α
-
k
(
R
)
*
(
i
)
.
10. The method of claim 7 wherein the step of estimating the unknown parameters comprises estimating the matrices A k , B k ,C k ,D k using the pre-defined training sequence wherein
(
r
k
,
0
…
r
k
,
L
-
1
)
=
(
A
k
B
k
C
k
D
k
)
(
e
j
ϕ
0
x
k
,
0
e
j
ϕ
1
x
k
,
1
…
e
j
ϕ
(
L
-
1
)
x
k
,
L
-
1
e
-
ϕ
0
x
k
,
0
e
-
j
ϕ
1
x
k
,
1
…
e
-
j
ϕ
(
L
-
1
)
x
k
,
L
-
1
e
j
ϕ
0
x
-
k
,
0
*
e
j
ϕ
1
x
-
k
,
1
*
…
e
j
ϕ
(
L
-
1
)
x
-
k
,
L
-
1
*
e
-
j
ϕ
0
x
-
k
,
0
*
e
-
j
ϕ
1
x
-
k
,
1
*
…
e
-
j
ϕ
(
L
-
1
)
x
-
k
,
L
-
1
*
)
R
=
EM
where R is a N rx ×L matrix, E is a N rx ×4N tx matrix and M is a 4N tx ×L matrix.
11. The method of claim 10 comprising estimating the matrices A k ,B k ,C k ,D k using a least-squares estimation method in accordance with
Ê=RM H ( MM H ) −1
where H indicates a complex conjugate transpose.
12. A method of compensating for in-phase quadrature (IQ) imbalance in a communication system comprising a transmitter and a receiver, the method comprising:
estimating the IQ imbalance in accordance with claim 1 ;
instructing the transmitter to use the estimated transmitter IQ (TX IQ) imbalance to pre-distort a transmitted signal to remove the effect of the TX IQ imbalance; and
instructing the receiver to use the estimated receiver IQ (RX IQ) imbalance to compensate a received signal to remove the effect of the RX IQ imbalance.
13. An electronic apparatus comprising a processor and a memory, the processor coupled to the memory and configured to:
define a system model in which a transmitted signal is affected by transmitter in-phase and quadrature (TX IQ) imbalance, carrier frequency offset (CFO) and receiver in-phase and quadrature (RX IQ) imbalance;
control a local oscillator at the transmitter to introduce a known carrier frequency offset (CFO) during a calibration; and
estimate unknown parameters in the system model using a pre-defined training sequence to determine the TX TO imbalance and the RX IQ imbalance,
wherein the CFO is chosen to provide a relative frequency offset of at least 0.001, at least 0.005 or at least 0.05.
14. The electronic apparatus of claim 13 configured as a mobile phone base-station, a digital video broadcasting (DVB) transmitter, a wideband wireless transmitter or a millimetre wave point-to-point transmitter.
15. An electronic apparatus comprising a processor and a memory, the processor coupled to the memory and configured to:
define a system model in which a transmitted signal is affected by transmitter in-phase and quadrature (TX IQ) imbalance, carrier frequency offset (CFO) and receiver in-phase and quadrature (RX IQ) imbalance;
control a local oscillator at the transmitter to introduce a known carrier frequency offset (CFO) during a calibration; and
estimate unknown parameters in the system model using a pre-defined training sequence to determine the TX IQ imbalance and the RX IQ imbalance,
wherein the TX IQ imbalance is defined as
y
k
,
l
(
i
)
=
α
k
(
T
)
(
i
)
x
k
,
l
(
i
)
+
β
-
k
(
T
)
*
(
i
)
x
-
k
,
l
*
(
i
)
where k indicates a subcarrier, l indicates a time index, i=1, . . . , N tx is a transmit channel index and α k (T) , β k (T) are IQ imbalance coefficients at the transmitter.
16. An electronic apparatus comprising a processor and a memory, the processor coupled to the memory and configured to:
define a system model in which a transmitted signal is affected by transmitter in-phase and quadrature (TX IQ) imbalance, carrier frequency offset (CFO) and receiver in-phase and quadrature (RX IQ) imbalance;
control a local oscillator at the transmitter to introduce a known carrier frequency offset (CFO) during a calibration; and
estimate unknown parameters in the system model using a pre-defined training sequence to determine the TX IQ imbalance and the RX IQ imbalance,
wherein the system model further comprises an inter-channel interference defined as
z
k
,
l
(
m
)
=
∑
i
=
1
N
tx
h
k
(
m
,
i
)
y
k
,
l
(
i
)
where m=1, . . . , N rx is a receive channel index and h is a channel coefficient.
17. An electronic apparatus comprising a processor and a memory, the processor coupled to the memory and configured to:
define a system model in which a transmitted signal is affected by transmitter in-phase and quadrature (TX IQ) imbalance, carrier frequency offset (CFO) and receiver in-phase and quadrature (RX IQ) imbalance;
control a local oscillator at the transmitter to introduce a known carrier frequency offset (CFO) during a calibration; and
estimate unknown parameters in the system model using a pre-defined training sequence to determine the TX IQ imbalance and the RX IQ imbalance,
wherein the CFO is defined as
w k,l ( m )= e jϕl z k,l ( m )
where ϕ represents a phase shift caused by the CFO.Cited by (0)
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